1. Field of the Invention
The present invention relates to a magnet member cutting method and a magnet member cutting apparatus, and more specifically to a magnet member cutting method and a magnet member cutting apparatus for cutting a magnet member by using a cutting blade having a cutting edge including abrasive grain and heat resistant resin for example.
2. Description of the Related Art
A conventional magnet member cutting apparatus uses a cutting blade comprising a base plate having an outer circumferential edge bonded with a mixture of diamond abrasive grain and resin. The resin plays an important part in cutting performance of the cutting blade.
Specifically, when cutting, if the resin is worn too soon, then the diamond abrasive grain is exposed one after another to a surface of the cutting edge, making a smooth cut surface of the magnet member, but the quick wear of the cutting blade makes a life of the cutting blade very short, leading to high cost.
On the other hand, when cutting, if the resin is worn too slowly, then the diamond abrasive grain is not exposed easily to the surface of the cutting edge, making the life of the cutting blade long but the quality of the cut surface is decreased. This problem becomes particularly significant when cutting a hard and brittle member such as a rare-earth magnet comprising a primary phase and a grain boundary phase. Further, because the rare-earth magnet is more expensive than a ferrite magnet, for the sake of cutting yield, a thin cutting blade having a blade thickness of 0.6 mmxcx9c1.0 mm and an outer diameter of 125 mm for example, is used. Therefore, if cutting ability of the cutting blade decreases, the quality of cut surface decreases drastically.
Further, there is inconsistency in the life of the cutting blade and quality of a cut surface; for example, the life of the cutting blade becomes shorter in a certain period of year, or the quality of the cut surface decreased in a certain time period of day.
It is therefore a primary object of the present invention to provide a magnet member cutting method and a magnet member cutting apparatus capable of increasing the life of the cutting blade life while improving the quality of the cut surface.
According to an aspect of the present invention, there is provided a magnet member cutting method comprising: a first step of preparing a cutting blade having a cutting edge including abrasive grain and heat resistant resin; and a second step of cutting a magnet member by the cutting blade while supplying temperature-controlled coolant to a cutting region.
According to another aspect of the present invention, there is provided a magnet member cutting apparatus comprising: temperature controlling means for temperature control of a coolant; coolant supplying means for supply of the coolant at a temperature controlled by the temperature controlling means to a cutting region; and cutting operation means for cutting the magnet member by using the cutting blade having a cutting edge including abrasive grain and heat resistant resin while the coolant is supplied by the coolant supplying means to the cutting region.
According to still another aspect of the present invention, there is provided a magnet member cutting apparatus comprising: temperature controller for temperature control of a coolant; coolant supplying path for the coolant at a temperature controlled by the temperature controller; a coolant discharging device for supply of the coolant from the coolant supplying path to a cutting region; and cutting operation portion for cutting the magnet member by using the cutting blade having a cutting edge including abrasive grain and heat resistant resin while the coolant is supplied by the coolant discharging device to the cutting region.
According to still another aspect of the present invention, there is provided a rare-earth magnet obtained by a magnet member cutting method comprising: a first step of preparing a cutting blade having a cutting edge including abrasive grain and heat resistant resin; and a second step of cutting a magnet member by the cutting blade while supplying temperature-controlled coolant to a cutting region.
According to the present invention, the magnet member is cut by the cutting blade while supplying the cutting region with the coolant at a temperature controlled in accordance with the heat resistant resin. By controlling the temperature of the coolant, the amount of wear of the heat resistant resin at the time of cutting can be controlled. Therefore, if the temperature of the coolant is controlled appropriately, the heat resistant resin wears appropriately at the time of cutting, letting the worn abrasive grain fall off to allow new abrasive grain to be exposed to the surface, thereby continuously maintaining the state in which the abrasive grain is exposed. As a result, the life of the cutting blade can be increased, the quality of the cut surface is improved, and production efficiency can be improved. The present invention is especially effective when obtaining a rare-earth magnet.
Preferably, the coolant is used in circulation. In this case, an amount of coolant consumption can be decreased, making possible to save the coolant. When the coolant is used in circulation, heat accumulation in the coolant usually becomes intense; however, according to the present invention, by controlling the temperature of the coolant, the coolant of a desired temperature can be supplied to the cutting region. As described above, the present invention offers significant effect when the coolant is used in circulation.
Further, preferably, the abrasive grain used in the cutting blade is a super hard abrasive grain such as diamond abrasive grain. In this case, chipping of the cutting edge is reduced at the time of cutting, and when the exposed abrasive grain has been worn, new abrasive grain from beneath has already exposed, leading to improvement in the quality of the cut surface.
Further, preferably, the heat resistant resin used in the cutting blade is a phenol resin. In this case, heat at the time of cutting makes the phenol resin be worn appropriately at the cutting region, facilitating the exposure of the new abrasive grain, leading to improvement in the quality of the cut surface.
Preferably, the temperature of the coolant is 20xc2x0 C.xcx9c35xc2x0 C. If the temperature of the coolant supplied to the cutting region is lower than 20xc2x0 C., the phenol resin remains hard and therefore not easily be worn, preventing the new abrasive grain from appropriate exposure and reducing the cutting ability. Thus, the cutting is continued with a dull cutting edge, reducing the cutting accuracy. On the other hand, if the temperature of the coolant exceeds 35xc2x0 C., the phenol resin becomes too soft. Therefore, although the new abrasive grain is exposed, the phenol resin is worn too quickly to support the abrasive grain, resulting in premature falling of the abrasive grain and early wear of the cutting edge, which is economically not preferable. Further, the cutting blade must be replaced more often, resulting in decrease in operating efficiency. As a result, the temperature of the coolant should be desirably 20xc2x0 C.xcx9c35xc2x0 C., at which the magnet member can be cut appropriately, with improved quality of the cut surface.
Further, preferably, the rotating speed of the cutting blade is 1000 m/minxcx9c3000 m/min. If the rotating speed of the cutting blade is slower than 1000 m/min, the cutting time becomes too long, and the cutting blade is deformed by idle rotation. On the other hand, if the rotating speed of the cutting blade exceeds 3000 m/min, an air flow accompanying the rotation prevents sufficient supply of the coolant to the cutting region, causing seizure of the cutting blade.
Further, preferably, a volume rate of the abrasive grain to the cutting edge is 10%xcx9c50%. If the volume rate of the abrasive grain is lower than 10%, the amount of the abrasive grain is too small and the cutting ability becomes extremely low. On the other hand, if the volume rate of the abrasive grain exceeds 50%, the amount of the abrasive grain is too much, resulting in decreased binding by the resin and therefore excessive fall of the abrasive grain, which reduces the life of the cutting blade.
Preferably, the cutting edge further includes metal powder. In this case, heat resistance and strength of the cutting blade can be increased.
The present invention is suitable to the cutting of a sintered rare-earth magnet member. When the sintered rare-earth magnet member is cut, cutting load is large, but by controlling the temperature of the coolant, the cutting load can be decreased, and the quality of the cut surface can be improved.
The above objects, other objects, characteristics, aspects and advantages of the present invention will become clearer from the following description of embodiments to be presented with reference to the accompanying drawings.